What socket is the red button at the window head?

Emergency call socket. The red circle next to the bedside socket is the emergency call socket. The keyhole shaped hole under the red button is the reset hole of the switch. The key of some alarm switches is to disarm the alarm. For example, the alarm switches of some high-end apartments are connected to the security monitoring room of the property. If there is an emergency, you can ask the security guard for help through it.